Improved polyethylene-coated paper photographic material

ABSTRACT

The bonding between the hydrophobic surface of a polyethylenecoated paper and the hydrophilic colloids used as binders for light-sensitive photographic emulsions can be established by means of an intermediate layer combination which comprises a layer of polymeric carbonic acid esters immediately coated on the polyethylene surface of the paper and a bonding layer of mixed acetals of polyvinyl alcohol and aldehydes with and without water-solubilizing groups.

United States Patent Inventors Priority Justus Danh'aiuser Koeln-Stammheim;

Peter Kruck, Koeln-Stammheim; Werner Krafft, Leverkusen, all of Germany 876,106

Nov. 12, 1969 Oct. 26, 1971 Agfa-Gevaert Aktiengesellschaft Leverkusen, Germany Nov. 19, 1968 Germany IMPROVED POLYETHYLENE-COATED PAPER PHOTOGRAPHIC MATERIAL 4 Claims, N0 Drawings US. Cl

Int. Cl

Field of Search 96/85, 96/87 R G03c 1/86 96/85, 87

[56] References Cited UNITED STATES PATENTS 3,025,163 3/1962 Ossenbrunner et al. 96/87 3,243,297 3/1966 Klockgether et a1 96/87 3,352,679 11/1967 Salminen 96/87 X 3,411,908 11/1968 Crawford et al.. 96/85 X 3,520,242 7/1970 Kemp et al 96/85 X Primary Examiner-Ronald H. Smith Attorney-Connolly and l-lutz IMPROVED POLYETHYLENE-COATED PAPER PHOTOGRAPHIC MATERIAL IMPROVED PHOTOGRAPHIC MATERIAL The invention relates to a photographic material having a nontransparent layer support of paper coated with polyethylene.

The use of polyethylenecoated paper as a layer support for photographic materials has been known for some time. This material differs from ordinary paper in that at least one of the two surfaces of the paper which consists of hydrophilic cellulose fibers is coated with thin foils of polyethylene. The advantage of such a support material is obvious. The solutions of the processing baths customarily used in photographic practice can then no longer penetrate the felt of the paper which has been rendered hydrophobic on the surface This results in shorter washing and drying times, especially in high-speed processes.

The polyethylene layers may be very thin so that the optical properties which depend on the surface structure of the paper are not significantly altered by the polyethylene coating. The polyethylene may also be rendered dull to improve the sharpness of the image.

This advantage, however, is offset by the disadvantage that the hydrophilic, light-sensitive colloid layers which usually consist of gelatine, polyvinyl alcohol and/or other binders will only adhere with difficulty, if at all, to this hydrophobic support.

Various proposals have been made to overcome this disadvantage.

Thus, for example polyethylene surfaces can be rendered hydrophilic by treating them with oxidizing agents such as H HNO C1,, HOCl etc. or by treating them with sulfuric acid and substances which act as oxidizing agents in the presence of sulfuric acid. Bonding layers of gelatin which may have other macromolecular substances added to them may then be applied to these hydrophilic surfaces.

Furthermore, polyethylene surfaces may be coated with bonding layers if they are fist subjected to electron radiation, for example, by means of a corona discharge. The effect of irradiation can be determined by the boundary angle which the polyethylene surface fonns with the surface of a drop of water applied to it. Polyethylene which has not been irradiated has a boundary angle of more than 90 which is reduced to 4075 after irradiation, which is sufficient for the activation required for applying a layer which will adhere firmly to the support.

It was found to be a disadvantage of this process that the activation achieved by electron radiation diminishes significantly within a short time, so that the light-sensitive emulsion or at least a gelatin-bonding layer must be applied to the polyethylene-coated paper immediately after the irradiation with electrons.

Other possibilities for activating polyethylene surfaces to allow hydrophilic colloid layers or other bonding layers to be applied lie in the treatment with oxidizing flames.

All these processes, however, involve great expenditure of apparatus and do not satisfy practical requirements in all respects.

It was therefore an object of the invention to provide a photographic material having a layer support of polyethylenecoated paper and at least one light-sensitive layer firmly adherent to the support.

A photographic material having a layer support of polyethylene-coated paper, an intermediate layer combination and at least one light-sensitive layer has now been found in which the intermediate layer combination comprises a layer of polymeric carbonic acid esters and a bonding layer.

The polimeric carbonic acid esters which may be used according to the invention are derived from aromatic dihydroxy compounds but, in particular, from bis-(hydroxyaryl)-alkanes in which the aryl groups may be substituted, e.g. by

monovalent, straight-chain or branched chain alkyl radicals containing up to 5 carbon atoms or by monovalent cycloalkyl or aryl radicals or by halogen atoms, such as chlorine or bromine and in which alkanes may also be cycloalkanes. The polymeric carbonic acid ester derived from 2,2-bis-( 4-hydroxyphenyl)-propane has proved to be' particularly suitable.

Polymeric carbonic acid esters used according to the invention may be prepared in known manner from the said dihydroxy compounds by reacting them with aliphatic or aromatic diesters of carbonic acid or with phosgene or with bischloro-carbonic acid esters of aromatic dihydroxy compounds by processes such as those described, for example, in the following US. Pat. specifications Nos: 2,946,766, 3,022,272, 3,028,365 and 3,136,741 and the English Pat. specification No. 808,490.

The polymeric carbonic acid esters may not only be used on their own but also in admixture with other synthetic resins, provided that they are compatible with these resins. As examples of such added synthetic resins, nitrocellulose, ethyl cellulose or copolymers of ethylene and vinyl acetate may be mentioned.

Application of the intermediate layer of polymeric carbonic acid esters may be carried out by immersion or surface application processes. Suitable solvents-for the polycarbonates for this purpose are methylene chloride, chloroform and in particular mixtures of these halogenated hydrocarbons with aromatic hydrocarbons such as benzene, toluene or xylene.

The polycarbonate layer adheres surprisingly firmly to the polyethylene layer. This effect is all the more surprising since it is well known that polyethylene and polycarbonate do not mix well with each other and that there is practically no solvent available for polyethylene.

A bonding layer which is to provide a bond between the hydrophobic support and the light-sensitive layer of hydrophilic colloids is applied to the polycarbonate intermediate layer in known manner.

This may be done, for example, by treating the support with a solution which contains a mixed acetal of polyvinyl alcohol and aldehydes with water-solubilizing groups and aldehydes--- without water-solubilizing groups. This mixed acetal is soluble in organic solvents and swells strongly in water.

Mixed acetals can be obtained by a conventional process, e.g. by heating the components for several' hours ,inl a methanolic solution with sulfuric acid as catalyst. Examples of aldehydes which have water-solubilizing groups are those which contain sulfonic acid, carboxy or hydroxyl groups in the aromatic nucleus, e.g. 4-sulfobenzaldehyde and 4-hydroxybenzaldehyde. Examples of aldehydes without water-solubilizing groups are aromatic, araliphatic and aliphatic aldehydes, e.g. benzaldehyde, tolyl aldehyde, 4 and hydrocinnamic aldehyde.

The acetalization must not be performed completely, and the mixed acetals can still contain free hydroxy groups. The degree of acetalization can be varied within wide limits. However, the best results are obtained if 50-60 percent of all hydroxy groups of the polyvinyl alcohol are acetalized. Suitable mixed acetals are described for example in US. Pat. specification No. 3,243,297.

Small quantities of a partly saponified copolymer of vinyl choloride and an organic vinyl ester such as vinyl acetate, vinyl propionate or vinyl butyrate, e.g. a partly saponified copolymer of vinyl chloride and vinyl acetate, may be added to the mixed acetals to improve the bonding effect. These...

partly saponified copolymers are prepared by known processes by saponification in methanol with sulfuric acid as catalyst, only the organic ester groups being partly saponified. Suitable saponified copolymers contain approximately 45-70 percent by weight of vinyl chloride, 5-30 percent by weight of vinyl alcohol and 10-40 percent by weight of vinyl ester. Copolymers of vinyl chloride and a, B-unsaturat'ed carboxylic acids or partly saponified copolymers of vinyl chloride and esters of the above-mentioned acid may also be used for this purpose.

Furthermore, additions of cross-linking agents also have an advantageous effect on bonding. The cross-linking agents used may be linear copolymers of unsaturated acid anhydrides with other polymerizable monomers, e.g. as described in US. Pat. specifications Nos. 2,047,398 and 2,913,437. Copolymers of establishes acetate and maleic acid anhydride having an acid anhydride content of 40-40 mols percent, based on the copolymer, are found to be especially advantageous.

To produce the bonding layer, the mixed acetal is applied to the polycarbonate intermediate layer by a dipping or surface application process in admixture with the above-mentioned copolymer and, if desired, with cross-linking agents. Suitable solvents are organic solvents, but in particular mixtures of acetone and methanol.

The invention will now be described by means of the following Example.

EXAMPLE A polyethylene-coated paper (layer thickness approximately 30 n) manufactured by the usual processes is treated with the following solutions by immersion:

l. 3 g. poly-2,2-bis-(4-hydroxphenyl)-propane-carbonate 100 ml. of chloroform 50 ml. of toluene,

After the application, the paper is dried at 50 to 90 C. and then treated with the the following solution:

2. 20 g. of polyvinyl alcohol mixed acetal of polyvinyl alcohol, benzaldehyde disulfonic acid sodium and benzaldehyde of the following composition:

Weight per cent Benzaldehyde disulfonate acetal 33.5 benzaldehyde acetal 35.2 vinyl alcohol 31.3

3 g. of a partly saponified copolymer of vinyl chloride and vinyl acetate of the following composition:

7 weight percent Vinyl chloride 63.2 vinyl alcohol 225.3

vinyl acetate 1 1.5

3 g. of a cross-linking agent having recurrent units of the following constitution: V V a V CHCH(|JHCBI (I) O=C =0 O=O (the polymer has a specific viscosity of 4.5 in a 1 percent solution in dimethylformamide at 20 'C.),

335 cc. of methanol 665 cc. of acetone. After the application, the layer is dried at 50-90 C. A silver halide emulsion poured on to this substrate layer adheres very firmly both in the wet and in the dry states.

We claim: 1. A photographic material having a nontransparent layer support of polyethylene-coated paper, an intermediate layer combination and at least one light-sensitive silver halide layer,

A in which the intermediate layer combination comprises a layer of polymeric carbonic acid esters based on bis-(hydroxyaryl)- alkanes and a bonding layer which establishes a bond with the light-sensitive layer.

2. A photographic material according to claim 1, which the intermediate layer combination comprises a layer of polymeric carbonic acid esters based on 2,2-bis-(4-hydroxyphenyl)- propane and a bonding layer.

3. A photographic material according to claim 1, in which the bonding layer contains mixed acetals of polyvinyl alcohol and aldehydes with water-solubilizing groups and those without water solubilizing groups in admixture with partly saponified copolymers of vinyl chloride and ester.

4. A photographic material according to claim 3 in which the bonding layer contains a cross-linking agent. 

2. A photoGraphic material according to claim 1, in which the intermediate layer combination comprises a layer of polymeric carbonic acid esters based on 2,2-bis-(4-hydroxyphenyl)-propane and a bonding layer.
 3. A photographic material according to claim 1, in which the bonding layer contains mixed acetals of polyvinyl alcohol and aldehydes with water-solubilizing groups and those without water solubilizing groups in admixture with partly saponified copolymers of vinyl chloride and ester.
 4. A photographic material according to claim 3 in which the bonding layer contains a cross-linking agent. 